The railroad industry employs a variety of freight railroad cars for transporting products. Many of these freight railroad cars such as box railroad cars and auto-rack railroad cars are enclosed to protect the products or vehicles being transported. These enclosed railroad cars typically include one or more sliding doors to provide access to the interior of these railroad cars. Many of these doors include hoods which are attached to the top or roof of the railroad cars by attachment assemblies such as pivot bolt assemblies for doors. As further described below, certain of these attachment assemblies tend to relatively quickly wear out and cause the doors to not work as intended or to malfunction.
Auto-rack railroad cars which transport newly manufactured vehicles such as automobiles, vans and trucks provide a prime example of this problem. Auto-rack railroad cars, referred to in the railroad industry as auto-rack cars, typically are compartmented, having two or three floors, a frame, two side walls, a roof, and a pair of doors at each end. The doors at each end protect the auto-rack car from illegal or unauthorized entry and thus prevent theft or vandalism of the vehicles being transported. The doors also prevent moving or flying objects from entering the auto-rack car and damaging the vehicles being transported. When unlocked, the doors are configured to be easily and quickly moved between closed and open positions to provide access to the vehicles in the auto-rack car. Examples of such auto-rack cars and the doors for auto-rack cars are generally illustrated in U.S. Pat. Nos. 3,995,563; 4,077,330; 4,917,021; 5,765,486; and 6,289,822. Auto-rack cars often travel thousands of miles through varying terrain. The movement of auto-rack cars causes movement and/or vibration of the individual components of the auto-rack cars including the roof and the doors. This movement and/or vibration causes substantial wear on certain components of the auto-rack cars including the known pivot bolt assemblies, the roof of the auto-rack cars and the hood of the doors of the auto-rack cars as discussed in more detail below.
FIGS. 1 and 2 generally illustrate a bi-level auto-rack car 20 including a frame 22 supported by trucks 24, each of which have several wheels 26 configured to roll along railroad tracks 28. The frame supports two side walls 30 and 32 and a roof 34. The auto-rack car 20 includes a pair of co-acting clamshell doors 36 and 38 mounted on each end of the auto-rack car. These doors are opened to facilitate the loading and unloading of vehicles into and out of the auto-rack car. Each of the end doors includes a substantially vertical panel 40 which extends from the floor to the roof and a pair of rollers (not shown) attached to the bottom of the panel for movably supporting the door. The top portions 42 and 44 of each of the doors are respectively pivotally connected to the roof by pivot bolt assemblies 46 and 48. Each pivot bolt assembly limits radial displacement of the door relative to its center of rotation. Each pivot bolt assembly also limits outward movement of the upper part of the door. The end doors are typically made of steel. The top portion of each end door typically includes a substantially solid rigid steel plate which is riveted, bolted, welded, or otherwise fastened to the vertical main portion of the door. This steel plate is sometimes referred to in the industry as a hood.
More specifically, one known and widely commercially used pivot bolt assembly for auto-rack cars is illustrated in FIGS. 3 to 7. This pivot bolt assembly 50 includes: (a) a non-metallic bushing or ball socket 52 configured to be positioned in the socket or indentation 41 formed in the hood 42 of the door; (b) a non-metallic cup liner 54 configured to be positioned in the roof stiffener 35 on the roof 34; (c) a shoulder bolt 56 configured to extend through the ball socket 52, the hood 42, the cup liner 54, the roof stiffener 35, and the roof 34; (d) two wave washers 58a and 58b positioned on the shoulder bolt 56; and (e) a nut 60 attachable to the shoulder bolt 56. Such known shoulder bolts tend to wear out at two specific locations along its shaft. The first wear location is at or about the plane of the hood and the second wear location is at or about the plane of the roof stiffener.
When the current pivot bolt assembly, and specifically the shaft of the shoulder bolt is subjected to enough wear, the shoulder bolt can break. If the shoulder bolt breaks, the top of the door can become disconnected from the roof. In such case, the door may not move because the top and bottom door locks hold the door in place. However, once the door locks are disengaged to operate the door, the door can fall off the end of the railroad car and cause damage or injury. Additionally, when the shoulder bolts are worn, the worn shoulder bolts can cause the door to not function as desired or to malfunction. The worn shoulder bolts can also cause damage to the door, the hood of the door, the roof or the roof stiffener, and other components of the auto-rack car. The cup liners of the pivot bolt assemblies have also been known to wear out.
The hood is also subject to wear, and specifically, the area which defines the hole in the hood is subject to a substantial amount of wear. In many auto-rack cars, the hole in the hood is originally a one-half inch diameter. This hole becomes larger due to the wear caused by movement of the current pivot bolt assembly. In certain cases, this hole has become as large as two inches and the entire pivot bolt assembly can fall through the hood. When this occurs, the hood of the door needs to be completely replaced, which is time consuming and expensive.
Accordingly, such known pivot bolt assemblies must be routinely inspected for wear and such known pivot bolt assemblies often need to be replaced to avoid unwanted movement of the doors and to avoid complete failures of the pivot bolt assemblies which can cause the tops of the doors to become disconnected from the roof. The doors and the roofs must also be inspected and must also be sometimes repaired. These inspections, repairs and replacements are time consuming and expensive for the railroad industry.
Accordingly, there is a need for an improved railroad car door pivot bolt assembly.